U.S. patent application number 10/532625 was filed with the patent office on 2006-03-09 for device for treatment of exhaust of an internal combustion engine.
Invention is credited to Gudrun Bieder, Markus Buerglin, Johannes Schaller, Ilona Ullmann.
Application Number | 20060051276 10/532625 |
Document ID | / |
Family ID | 32115278 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060051276 |
Kind Code |
A1 |
Schaller; Johannes ; et
al. |
March 9, 2006 |
Device for treatment of exhaust of an internal combustion
engine
Abstract
A method and a device for treatment of the exhaust of an
internal combustion engine in which a fluid is used as an auxiliary
agent for the treatment; a partial chemical conversion of the
auxiliary agent is at least occasionally stimulated in order to
produce a substance that reduces the freezing point of the fluid
when the temperature of the fluid falls below a critical value.
Inventors: |
Schaller; Johannes;
(Leonberg, DE) ; Buerglin; Markus; (Ditzingen,
DE) ; Ullmann; Ilona; (Korntal-Munchingen, DE)
; Bieder; Gudrun; (Denkendorf, DE) |
Correspondence
Address: |
RONALD E. GREIGG;GREIGG & GREIGG P.L.L.C.
1423 POWHATAN STREET, UNIT ONE
ALEXANDRIA
VA
22314
US
|
Family ID: |
32115278 |
Appl. No.: |
10/532625 |
Filed: |
October 27, 2003 |
PCT Filed: |
October 27, 2003 |
PCT NO: |
PCT/DE03/03562 |
371 Date: |
April 25, 2005 |
Current U.S.
Class: |
423/235 ;
431/195 |
Current CPC
Class: |
F01N 2610/10 20130101;
B01D 53/9431 20130101; B01D 53/90 20130101; Y02T 10/12 20130101;
F01N 3/208 20130101; F01N 2610/1486 20130101; F01N 2610/02
20130101; Y02T 10/24 20130101; B01D 53/79 20130101; F01N 2900/1818
20130101; F01N 2900/1811 20130101 |
Class at
Publication: |
423/235 ;
431/195 |
International
Class: |
F23D 5/00 20060101
F23D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2002 |
DE |
102 51 588.3 |
Claims
1-13. (canceled)
14. A method for treatment of the exhaust of an internal combustion
engine in which a fluid is used as an auxiliary agent for the
treatment, the method comprising the steps of at least occasionally
stimulating a partial chemical conversion of the auxiliary agent in
order to produce a substance that reduces the freezing point of the
fluid when the temperature of the fluid falls below a critical
value.
15. The method according to claim 14, wherein the conversion of the
auxiliary agent is stimulated before the auxiliary agent is
introduced into the exhaust.
16. The method according to claim 14, wherein the fluid is drawn
from a tank and supplied to the exhaust via lines, and wherein the
stimulation occurs in a partial region of the tank or in a fluid
volume contained in the lines so that a sufficient quantity of the
substance can be distributed in the fluid volume in order to
achieve a uniform freezing point reduction.
17. The method according to claim 15, wherein the fluid is drawn
from a tank and supplied to the exhaust via lines, and wherein the
stimulation occurs in a partial region of the tank or in a fluid
volume contained in the lines so that a sufficient quantity of the
substance can be distributed in the fluid volume in order to
achieve a uniform freezing point reduction.
18. The method according to claim 14, further comprising the step
of supplying heat to produce the stimulation.
19. The method according to claim 16, further comprising the step
of supplying heat to produce the stimulation.
20. The method according to claim 17, further comprising the step
of supplying heat to produce the stimulation.
21. The method according to claim 19, wherein heat is supplied for
a time to heat the partial region of the fluid to a temperature
above 60.degree. Celsius.
22. The method according to claim 18, wherein due to a spatial
distribution, the supply of heat causes only a slight temperature
increase in the fluid volume over time.
23. The method according to claim 21, wherein due to a spatial
distribution, the supply of heat causes only a slight temperature
increase in the fluid volume over time.
24. The method according to claim 22, wherein the slight
temperature increase lies in the range between 5 Kelvin and 50
Kelvin.
25. The method according to claim 23, wherein the slight
temperature increase lies in the range between 5 Kelvin and 50
Kelvin.
26. The method according to claim 14, wherein the freezing point is
reduced by 10 to 30 Kelvin.
27. The method according to claim 14, further comprising the step
of measuring the concentration of the substance in the fluid and/or
the temperature of the fluid, and establishing the intensity and/or
duration of the stimulation as a function of the concentration of
the substance and/or the temperature.
28. The method according to claim 16, further comprising the step
of measuring the concentration of the substance in the fluid and/or
the temperature of the fluid, and establishing the intensity and/or
duration of the stimulation as a function of the concentration of
the substance and/or the temperature.
29. The method according to claim 18, further comprising the step
of measuring the concentration of the substance in the fluid and/or
the temperature of the fluid, and establishing the intensity and/or
duration of the stimulation as a function of the concentration of
the substance and/or the temperature.
30. The method according to claim 27, wherein the concentration
and/or the temperature is measured in the partial region.
31. The method according to claim 14, wherein the substance is a
gas that is soluble in the fluid.
32. The method according to claim 14, wherein a urea/water solution
is used as the fluid and ammonia is the substance.
33. A device for treatment of the exhaust of an internal combustion
engine in which a fluid (1) is used as an auxiliary agent for the
treatment, the device comprising means (2, 3, 4, 5, 3a, 4a, 5a, 14)
for at least occasionally stimulating a partial chemical conversion
of the auxiliary agent into a substance that reduces the freezing
point of the fluid, the means being disposed and/or embodied so as
to permit the stimulation to occur when the temperature of the
fluid falls below a critical value.
Description
PRIOR ART
[0001] The invention is based on a method and a device for
treatment of the exhaust of an internal combustion engine, as
generically defined by the preamble to the independent claims. A
method and a device of this kind are already known from DE 199 35
920, in which in order to prevent a urea/water solution from
freezing at -11.degree. C., heating tubes are provided in the
reducing agent reservoir so that the reducing agent reservoir can
be heated when reducing agent temperatures fall below 20.degree.
C.
ADVANTAGES OF THE INVENTION
[0002] The method and device according to the present invention,
with the characterizing features of the independent claims, have
the advantage over the prior art of achieving a reduction in the
freezing point of the fluid through concerted use of a conversion
reaction of the auxiliary agent, in particular a decomposition
reaction, without having to accept an appreciable temperature
increase in the fluid system. At low outside temperatures, constant
reheating is no longer necessary because after a concerted chemical
conversion, ice no longer forms, even at low temperatures, and the
heating does not have to be activated as long as the fluid contains
a sufficient concentration of the substance produced by the
conversion reaction.
[0003] Advantageous modifications and improvements of the methods
and devices disclosed in the independent claims are possible by
means of the steps taken in the dependent claims.
[0004] It is particularly advantageous to carry out the stimulation
in a partial region of the fluid volume contained in the tank
and/or in lines so as to effectively enrich the fluid with the
substance, without appreciably increasing the average temperature
of the fluid.
[0005] It is easy to use the concerted decomposition of urea into
ammonia to prevent the danger of freezing and thus the attendant
risk of damage to lines and/or other system components, despite low
outside temperatures and despite only an insignificant increase in
the temperature of the fluid on average chronologically and
spatially.
[0006] Other advantages ensue from other characteristics disclosed
in the dependent claims and mentioned in the specification.
DRAWING
[0007] Exemplary embodiments of the present invention are shown in
the drawing and will be explained in greater detail in the
subsequent description.
[0008] FIG. 1 shows a system for selective catalytic reduction of
nitrogen oxides in the exhaust of an internal combustion
engine.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0009] In the sole FIG. (1), the exhaust line 9 represents the
exhaust line of an internal combustion engine, in particular a
diesel engine of a motor vehicle. The exhaust 16 flows from the
internal combustion engine through the exhaust line 9, passes a
urea/water solution line (UWS line) 8 connected to the exhaust line
9, and finally arrives in a catalytic converter, not shown in
detail, for selective catalytic reduction of nitrogen oxides
contained in the exhaust. Downstream of the SCR catalytic converter
("SCR"="selective catalytic reduction"), the exhaust flows through
other devices, not shown in detail, for example other catalyzing
units and/or a muffler, into the open-air. At the end opposite from
the region feeding into the exhaust line, the UWS line 8 is
connected to a urea/water solution tank 10. Between the tank 10 and
the exhaust line 9, the line 8 contains a pump 6 and, between the
pump 6 and the exhaust line 9, a metering valve 7 that can be
cyclically triggered. The tank 10 contains a urea/water solution
(UWS) with a urea content of for example 32.5% by weight. In a
partial volume 13 of the tank 10 that is disposed in the lower
region of the tank in the current exemplary embodiment, an
electrical heater 3 is provided; the supply of electrical power to
the heater of the UWS in the partial volume is schematically
indicated by the letters P.sub.EL. On the upper side oriented
toward the surface of the urea/water solution in the tank, a
separating element 2 that is fastened to the side region of the
tank forms an upper boundary of the heater 3, which is embodied as
an electric heating coil. This boundary serves to define the region
in which a significant heating or temperature increase of the fluid
in the tank can occur. Lateral to the separating element and
adjacent to it, a temperature sensor 4 and an ammonia sensor 5 are
provided in order to determine the temperature and the ammonia
concentration in the heatable partial volume. Above the fluid level
of the urea/water solution, the tank 10, which can be closed by
means of a closure device not shown in detail, is equipped with a
pressure relief valve 11 that allows excess gas pressure to escape
via a washing bottle 12 to which it connects. In addition, an
electronic control unit 14 is provided that calculates, among other
things, the intrinsically known functions of metering the
urea/water solution into the exhaust train as a function of engine
and/or exhaust parameters that are supplied to the control unit in
a manner not shown in detail after being measured in the engine or
exhaust train. In addition, this control unit 14 is connected to
the temperature sensor 4 in order to evaluate a temperature signal
4a and is connected to the ammonia sensor 5 in order to evaluate an
ammonia concentration signal 5a. A control signal line 3a can, for
example, trigger a power transistor circuit, not shown in detail,
in order to regulate the electrical heating capacity of the
electric heater 3.
[0010] The pump and the metering valve 7 are triggered via
triggering lines, not shown in detail, that are connected to the
control unit 14 to supply a urea/water solution in an intrinsically
known fashion to the exhaust 16 in a metered form in order to
achieve, in the NOx-reduction catalytic converter not shown in
detail below, a reduction of the nitrogen oxides contained in the
exhaust in accordance with the method of selective catalytic
reduction. In this connection, within the exhaust train, ammonia is
derived from the urea/water solution supplied to the exhaust train
and this ammonia selectively reacts with the nitrogen oxides in the
SCR catalytic converter to produce nitrogen and water. In addition
to the complete conversion of the urea/water solution into ammonia
in the region of the exhaust train, in a partial region of the
urea/water solution system comprised of the tank 1, line 8, pump 6,
and metering valve 7, according to the present invention, the
urea/water solution in the partial volume 13 of the tank 10 is
heated to a decomposition temperature in a range above 60.degree.
C. in order to stimulate an occasional, limited, partial
decomposition reaction of urea to produce ammonia. The control unit
14 controls the heating capacity and the activation period of the
heater as a function of the temperature and ammonia concentration
values measured in the partial volume 13. This supply of heat
occurs when a critical temperature value is reached or exceeded,
which lies in a range from 0.degree. C. to -11.degree. C.,
preferably in a range from -5.degree. C. to -10.degree. C. In this
connection, care is taken to assure a sufficiently high ammonia
concentration in the entire fluid volume of the urea/water solution
system in order to achieve a sufficiently significant reduction in
the freezing point so that a subsequent reheating can be avoided
even if the temperature falls below the critical value again.
However, if the ammonia concentration has decreased to the point
that a sufficient reduction in the freezing point is no longer
assured, then the heating must be switched on again when the
temperature falls below the critical temperature value. The ammonia
concentration normally fluctuates in a range of between 7 and 20
percent, thus yielding a freezing point reduction in a range from
10K and 50K. It is particularly advantageous to establish a value
of approx. 7 to 15 percent by volume of ammonia in the urea/water
solution in order to reduce the freezing point of the urea/water
solution from -11.degree. C. to a range from -20.degree. C. to
-30.degree. C. The temperature of the urea/water solution is raised
by 5K to 50K on average chronologically and spatially, and the
pressure in the tank increases only slightly. The pressure relief
valve 11 blows off any excess pressure generated by the escape of
ammonia from the urea/water solution. Before the excess pressure is
released into the environment, the gas passes through the washing
bottle 12, by means of which the ammonia contained in the gas can
be removed from the escaping gas in order to minimize the risk of
environmental damage due to escaping ammonia. Up to 700 l of
ammonia can be dissolved in 1 l of water. In the current exemplary
embodiment, the tank volume is 60 l, so that at atmospheric
pressure, 10 times the tank volume in pure ammonia can be dissolved
in 1 l of water contained in the washing bottle 12. Either the
state of the water in the washing bottle is monitored by means of
devices not shown in detail or the water is replaced at regular
intervals (for example after a fixed number of tank refills).
[0011] In an alternative embodiment form, the escape of excess
pressure in the tank 10 is not conveyed into the environment, but
rather into the exhaust line in order for ammonia that may have
passed through the washing bottle 12 to still be neutralized in the
SCR catalytic converter and to assure an additional degree of
certainty in preventing environmental damage. In an improved
embodiment form, the method for the concerted decomposition of urea
into ammonia in the region of the UWS system for freezing point
reduction can include an additional measurement of the outside
temperature so that a freezing point reduction is activated only
when necessary, i.e. at low outside temperatures, particularly in
the subzero range. The heating of a partial region of the UWS
volume and the stimulation of a decomposition of urea into ammonia
in a partial region of the UWS system can also be carried out in a
part of the system other than the tank. When using a metering valve
7 in the form of an injection valve cooled with the urea/water
solution, it is also possible to powerfully throttle the coolant
flow of the urea/water solution so that the urea/water solution
used as the coolant is heated in the desired fashion to stimulate
the urea decomposition. The ammonia sensor here can, for example,
be disposed in the tank while the temperature sensor is disposed in
the coolant flow. This alternative, not shown in detail, comprised
of also using the urea/water solution as a coolant for cooling the
metering valve disposed in close proximity to the exhaust train
while providing a throttling of the coolant flow, can be further
improved by embodying this throttling as controllable, in
particular so that it can be controlled as a function of measured
urea/water solution temperatures or measured ammonia concentration
values. Furthermore, in another embodiment form, the pressure
relief valve 11 can be designed so as to permit a definite pressure
increase in the system, which shifts the chemical equilibrium
between urea and ammonia in the system further in the direction of
the ammonia gas. Alternatively, an auxiliary heating system can
also be used to locally heat the urea/water solution in a partial
region of the tank 10 or in a partial region of the exhaust line 8
in order to lighten the load on the vehicle battery, particularly
when the stimulation of the decomposition reaction is to also occur
during long stops, i.e. when the engine is switched off. In other
alternative embodiment forms, the method and the system can be
embodied and/or improved so that a temperature gradient that is
produced causes a mass transfer to occur in the system, in
particular between the heated partial region and the rest of the
tank region in order to be able to treat the entire urea/water
solution in relatively short periods of time through the local
supply of heat and to assure a rapid distribution of the generated
ammonia throughout the entire system. The better the system is
designed to encourage such a convection, the less energy is
required because the generated ammonia is immediately distributed
throughout the system and remains dissolved without immediately
escaping from the aqueous solution and therefore being unavailable
for reducing the freezing point.
* * * * *